(A) power-efficient, wide-frequency-range impedance measurement IC using frequency-shift technique

Abstract

This paper proposes an impedance-measurement integrated circuit (IC) that supports a high frequency range up to 10 MHz with low power consumption. The proposed IC extracts the magnitude and phase component of the target impedance, and a reference resistor is connected in series with the target impedance to provide a reference amplitude and time information without the delay of the voltage controlled current source of the transmitter. The chopper frequency-shift the input signal, which range above 100 kHz, to a intermediate frequency of 10 kHz at the front end of the receiver. Therefore, the requirements on the IA bandwidth and the comparator delay are loosed, so the overall power consumption is dramatically reduced. Moreover, the reference magnitude measurement path and auto-zeroing technique is added to achieve higher measurement accuracy. The chip fabricated in a 180-nm CMOS process consumes only 756 µW for a frequency range from 100 Hz to 10 MHz, and the measured magnitude and phase errors are less than 1.1% and 1.9º, respectively.